1. Field of the Invention
This invention relates to a thin film magnetic head, particularly to a magnetoresistive effective type thin film magnetic head and a method for fabricating the same.
2. Related Art Statement
As a magnetic conversion device employed in a hard disk driving device, a combination type thin film magnetic head, where an inductive type thin film magnetic head element for writing and a magnetoresistive effective type thin film magnetic head element are stacked on a given substrate in turn, is widely available. With the development of the surface recording density of such a hard disk driving device, the performance of such a combination type thin film magnetic head is required to be developed. As a magnetoresistive effective type thin film magnetic head element, an AMR element utilizing normal anisotropic magnetoresistive effect is usually employed, but recently, a GMR element utilizing giant magnetoresistive effect several times as large as the normal anisotropic magnetoresistive effect is developed and widely available.
In the AMR element, surface recording density of several giga bits/inch2 can be realized, and in the GMR element, the surface recording density can be more enhanced. As a result, a large capacity hard disk driving device having a capacity of several ten giga bits or over can be realized.
As of now, various types of GMR element are proposed, but particularly attention is paid to a spin-valve GMR element. In the spin-valve GMR element, longitudinal bias-applying films are formed in both sides of a magnetoresistive effective film (MR film). In some cases, both edges of the MR film are covered with electrode films. In this case, the distance between the electrode films is set smaller than the distance between the longitudinal bias-applying films. Such an element structure is usually called as a “lead overlay structure”, and is disclosed in Japanese Patent Applications Laid-open Hei 8-45037 (JPA 8-45037) and Hei 9-282618 (JPA 9-282618). Such a lead overlay structure is employed in an AMR element as well as the spin-valve GMR element. In a magnetoresistive effective type thin film magnetic head having such a lead overlay structure, Barkhausen noise can be repressed effectively and fluctuation in output power can be reduced. Therefore, the sensitivity of the thin film magnetic head can be enhanced.
In fabricating the magnetoresistive effective type thin film magnetic head having the lead overlay structure, two uniform films are formed and patterned to form the longitudinal bias-applying films and the electrode films, respectively. In this case, that is, two photolithography steps are required. Normally, the longitudinal bias-applying films are formed and thereafter, the electrode films are formed. As mentioned above, since the distance between the electrode films is set smaller than the distance between the longitudinal bias-applying films, the above photolithography steps are difficult and thus, the longitudinal bias-applying films and the electrode films can not be patterned precisely.
Particularly, in forming the electrode films, the surface level of the MR film is different from the surface level of the longitudinal bias-applying films. Therefore, it is more difficult to form the electrode films precisely due to the steps created between the MR film and the longitudinal bias-applying films, so that the magnetoresistive effective type thin film magnetic head can not be fabricated stably on a wafer as a substrate.